A young man known as "Bloody Cross", with silver eyes and black hair who has protected Yuki from the shadows since Yuki's birth 15 years ago. Despite being a duras, he is currently acting alongside the Gioh family. Though his true age is unknown, in human terms he appears to be a university student. Normally reserved and expressionless, Luka's facial expression softens around Yuki. It was during the Last Battle that Luka defected over to the humans. In the previous era, he and "female" Yuki were lovers.

Luka battles with a large black sword and can use powerful magic (and even summon a powerful Salamander dragon). He was once the loyal dog for the demon king and used to drink his blood, that's why he is stronger than any opasts and it's possible that he is stronger than the demon king himself. But he left his position as the loyal dog for the demon king after meeting Yuki. It was during the previous battle that Luka met Yuki and they fell in love. The current Yuki doesn't remember being Luka's lover, but every time he sees Luka his heart responds strongly. Luka refuses to tell Yuki about their past, but stands by the current male Yuki and promises he will stay with Yuki as long as Yuki wants him to.

The manga suggests a bit of a darker history. Luka tells Yuki he was considered a slave because he belonged to the "sinner" clan, Crosszeria, and that all the other duras were intent on punishing the whole family and all its descendants. The demon king owned Luka, and as a symbol of this, put his own blood into Luka's brand. The demon king's blood made the brand on Luka's arm glow red, and it caused Luka a great deal of pain during the process. Years later, Luka is still haunted by the memory and feels physically ill when recalling it. Because it was a blood seal, if Luka should ever betray the demon king, he would die. Luka explains to the current incarnation of Yuki that since he made a new contract with Yuki, the previous contract with the demon king was voided, allowing Luka to live. Luka hints that the prior contract with the demon king may not be "completely" voided, however.